Hard material such as a metal, dental material, such as filling material or dental prosthesis material, or a hard bio-tissue, for example tooth enamel dentine or bone, has heretofore been ablated or otherwise processed by directing optical radiation, and in particular, laser radiation, at the material. However, the inventors have found that such procedures have in the past been less optimally efficient for a number of reasons.
In particular, where a laser, for example an Er laser, is being used to ablate bio-tissue such as tooth enamel, the efficiency of the ablation can be significantly enhanced by assuring adequate water content on the surface of the material being treated and by keeping the irradiated surface of the material free of dirt. The first condition is important because water collected in natural cavities and in micro-cracks produced in the material due to laser treatment may expand as a result of irradiation, thereby assisting in the ablation process, and can also generate shock waves which also facilitate the process. The second condition is important to prevent dirt, including particles of ablation, from interfering with light flow to the tissue surface, such interference resulting both from such dirt blocking radiation from reaching target material and from absorption of radiation by such dirt. It has been found by the inventors that the second condition alone can increase ablation efficiency by roughly 30% to 500%. The two conditions together can result in a many-fold increase in efficiency.
However, hydrating and cleaning the tissue or other hard material during treatment is normally difficult where the light guide through which the radiation is applied to the material is in contact with the material, as is preferably the case, the light guide preventing water from reaching the tissue under the light guide for hydration, and preventing ablation products from leaving the area under the light guide. Except for embodiments such as that shown in copending application Ser. No. 09/549,406, or other embodiments where ablation products and other energy resulting from the ablation process are recycled, contact between the light guide and/or any particular other energy reflector rounding the light guide and the tissue during irradiation is usually desirable in that it results in less photon loss, and thus higher ablation efficiency. By hydrating, cleaning and recycling energy lost from the ablation process, optimum enhancement of ablation efficiency can be achieved, permitting smaller and less expensive radiation sources to be used for the material processing.
A need therefore exists for a method and apparatus which facilitates hydration and cleaning of hard material, and in particular hard tissue such as tooth enamel, during ablation/processing of the material, and which preferably also facilitates recycling of ablation products/lost energy, so as to optimize ablation/processing efficiency. Improved and novel laser sources which take advantage of the lower energy requirements resulting from the enhanced ablation efficiency to provide required energy with smaller and less expensive units are also desirable.